After much _____ the shop owner agreed to cut down the price by 20% . [ ]

A. debating

B. talking

C. discussing

D. bargaining

COPD患者氧疗有效的指标为（）。

A.血压下降

B.呼吸表浅、缓慢

C.发绀减轻

D.心率减慢

E.呼吸困难缓解